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FreeBSD-SA-16:01.sctp                                       Security Advisory
                                                          The FreeBSD Project

Topic:          SCTP ICMPv6 error message vulnerability

Category:       core
Module:         SCTP
Announced:      2016-01-14
Credits:        Jonathan T. Looney
Affects:        All supported versions of FreeBSD
Corrected:      2016-01-14 09:11:42 UTC (stable/10, 10.2-STABLE)
                2016-01-14 09:10:46 UTC (releng/10.2, 10.2-RELEASE-p9)
                2016-01-14 09:11:16 UTC (releng/10.1, 10.1-RELEASE-p26)
                2016-01-14 09:11:48 UTC (stable/9, 9.3-STABLE)
                2016-01-14 09:11:26 UTC (releng/9.3, 9.3-RELEASE-p33)
CVE Name:       CVE-2016-1879

For general information regarding FreeBSD Security Advisories,
including descriptions of the fields above, security branches, and the
following sections, please visit <URL:https://security.FreeBSD.org/>.

I.   Background

The Stream Control Transmission Protocol (SCTP) protocol provides reliable,
flow-controlled, two-way transmission of data. 

The Internet Control Message Protocol for IPv6 (ICMPv6) provides a way for
hosts on the Internet to exchange control information.  Among other uses,
a host or router can use ICMPv6 to inform a host when there is an error
delivering a packet sent by that host. 

II.  Problem Description

A lack of proper input checks in the ICMPv6 processing in the SCTP stack
can lead to either a failed kernel assertion or to a NULL pointer
dereference.  In either case, a kernel panic will follow.

III. Impact

A remote, unauthenticated attacker can reliably trigger a kernel panic
in a vulnerable system running IPv6.  Any kernel compiled with both IPv6
and SCTP support is vulnerable.  There is no requirement to have an SCTP
socket open.

IPv4 ICMP processing is not impacted by this vulnerability.

IV.  Workaround

No workaround is available, but systems using a kernel compiled without
SCTP support or IPv6 support are not vulnerable.

In addition, some stateful firewalls may block ICMPv6 messages that are
not responding to a legitimate connection.  (However, this may not
completely block the problem, as an ICMPv6 message could still be sent
in response to a legitimate SCTP connection.)

V.   Solution

Perform one of the following:

1) Upgrade your vulnerable system to a supported FreeBSD stable or
release / security branch (releng) dated after the correction date.
Rebooting to the new kernel is required.

2) To update your vulnerable system via a binary patch:

Systems running a RELEASE version of FreeBSD on the i386 or amd64
platforms can be updated via the freebsd-update(8) utility:

# freebsd-update fetch
# freebsd-update install

Rebooting to the new kernel is required.

3) To update your vulnerable system via a source code patch:

The following patches have been verified to apply to the applicable
FreeBSD release branches.

a) Download the relevant patch from the location below, and verify the
detached PGP signature using your PGP utility.

# fetch https://security.FreeBSD.org/patches/SA-16:01/sctp.patch
# fetch https://security.FreeBSD.org/patches/SA-16:01/sctp.patch.asc
# gpg --verify sctp.patch.asc

b) Apply the patch.  Execute the following commands as root:

# cd /usr/src
# patch < /path/to/patch

c) Recompile your kernel as described in
<URL:https://www.FreeBSD.org/handbook/kernelconfig.html> and reboot the
system.

VI.  Correction details

The following list contains the correction revision numbers for each
affected branch.

Branch/path                                                      Revision
- -------------------------------------------------------------------------
stable/9/                                                         r293898
releng/9.3/                                                       r293896
stable/10/                                                        r293897
releng/10.1/                                                      r293894
releng/10.2/                                                      r293893
- -------------------------------------------------------------------------

To see which files were modified by a particular revision, run the
following command, replacing NNNNNN with the revision number, on a
machine with Subversion installed:

# svn diff -cNNNNNN --summarize svn://svn.freebsd.org/base

Or visit the following URL, replacing NNNNNN with the revision number:

<URL:https://svnweb.freebsd.org/base?view=revision&revision=NNNNNN>

VII. References

<URL:https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2016-1879>

The latest revision of this advisory is available at
<URL:https://security.FreeBSD.org/advisories/FreeBSD-SA-16:01.sctp.asc>
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